HVAC - Fan only works on high

aberrant · 10-01-2010, 04:11 AM

I have the infamous "fan only works on high" problem. I've read many other threads on this topic, as it is very popular, but just wanted to share my story and throw out a checklist for discussion.

My fan has been working fine on all speeds since I've had the Jeep (purchased last year from original owner) and I don't think it has had any issues previously as I have all repair records. Yes, literally ALL of them. The PO was very meticulous. Anyways, the other day I had to bleed the air out of my cooling system, so per the advice of fellow board members, I parked the Jeep on an incline, removed the cap from the radiator and ran the fan on high heat. This is where I think my problem started. After this I noticed that when I used the AC, there was a very faint burning smell coming from the vents. I brushed it off as some outside influence as I didn't have the climate control on recirculate. I also thought it could have been some of the residual coolant that had overflowed onto the fan and radiator. However, after using the recirculated air mode, the burnt smell was still there. At this point I was a bit concerned, but left it again to see if it would go away on its own.

Well, today while driving down the highway, I had my AC going at the number 2 or 3 speed and then all of a sudden it just stopped. No burning smell at this point though. After trying the different modes to no avail, I realized the fan did work on the high setting just fine, But geeez that high setting is really HIGH! Since I can't live with just a high setting, which means either freeze or burn your *** off, I did some research on what the culprit could be. As many of you know, the blower motor resistor is often the issue. But before I start tearing my Jeep apart, ordering parts, and spending money I don't need to, I wanted to see if this list of things to check first is a good one.

Here's what I've gathered:

1. Check the fuses both F8 in the dash and F11 under the hood.
2. Check fan motor for wear, debris, etc. and see if starts up fine.
3. Check blower motor resistor. (Most likely the culprit in my case).
4. Check climate control switches for melting or burnt wires.

So that's my checklist as of now. Anything I'm missing?

Also, is it recommended to replace the fan itself as that could be the main problem? I don't want to replace the resistor and then have it fail 2 months down the road like others have reported. Aside from putting in the relays found in this thread, http://www.jeepforum.com/forum/f9/ac...elting-608645/, what's the best plan of action here?

I know this topic has been beat to death, but just wanted to throw out a checklist to go by.

Neil F. · 10-01-2010, 04:19 AM

High only is usually pretty cut and dry. The resistor. The Fan is not going to cause the resistor to go.

Brewz · 10-01-2010, 05:12 AM

My first thought also goes to the resistor. However since you smelt something burnt I would check the back of the switch first. Its easy to look at and may save you some time troubleshooting.

I had a switch melt and when it did I smelt burning electronics. (I can not remember if I had 1 speed right after that or not but it seems like I did for a very short period)

If it is the switch I have the part number at home for just the switch and not the whole control head that every shop wanted to replace.

Good luck,
Brewz

williambmac · 10-01-2010, 05:25 AM

The fan can in fact cause the resistor to go. It can also cause the fan speed switch to go.
After a period of time the fan motor starts to wear out. It is usually the bearings, the motor gets abit of drag to it.
This drag causes the motor to draw more amps. The jeeps less than adaquade electrical system starts to systematically fail.
Usually the resistor will loose speeds 1 thru 3 and you are left with hi speed only. After driving on high speed only the fan switch or the harness connector will usually burn up and fail.
I have replaced resistors, switches, connectors and wiring on numerous jeeps and it all boils down to the fan motor drawing to many amps.

**Knuckelhead** · 10-01-2010, 05:37 AM

Quote:

Originally Posted by Neil F.

The Fan is not going to cause the resistor to go.

Yes it will.

Quote:

Originally Posted by williambmac

it all boils down to the fan motor drawing to many amps.

Yes it does...

JBTJ · 10-01-2010, 05:43 AM

Your best plan of action would be to check everything like you said and then add the relays. It's not a big deal to do. Even if the resistor is bad and the switch is starting to melt like I think it is, and would check first, you still need to add the relays. Then save up and get a new blower motor later on. Also, the fact that you had to do work on the radiator has nothing to do with this problem.

williambmac · 10-01-2010, 06:58 AM

you can order a blower motor from these guys. 2000 Jeep Wrangler Heater Blower Motor with Fan Cage at 1AAuto.com.

I have dealt with them on several occasions and have been very pleased with their service. Beats the 160.00 price tag from the auto parts store.

Neil F. · 10-01-2010, 09:48 AM

Ok, stand corrected.

aberrant · 10-02-2010, 12:28 AM

Well, tore into my dash under the glovebox and replaced the resistor. It was in bad shape with rust and corrosion on it. I'm glad I replaced it when I did, as it looked like a fire hazard. It also had some leaves, and a couple pine needles in there which wasn't looking too good. How does that stuff get in there anyways? Kicked up from the floor? Seems like a HUGE fire hazard, and I know some people have had fires because of it. Anyways, all speeds work fine now. Hopefully my fan motor stays good and doesn't fry this resistor. What's the likelihood that it would?

Here's a couple photos of my resistor.